Finite amplitude distortion and its relationship to linear derating formulae for diagnostic ultrasound systems
Finite amplitude distortion and its relationship to linear derating formulae for diagnostic ultrasound systems
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DOI：
10.1016/s0301-5629(96)00099-3
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发表时间：
1996-01-01
影响因子：
2.9
通讯作者：
Carstensen, EL
中科院分区：
文献类型：
--
作者：
Christopher, T;Carstensen, EL
可以用作超声的生物效应的预测因子的指数的制定涉及称为降额的过程，其中在水中进行的声场的测量被外推到身体组织中的声场的幅度的估计。到目前为止已经制定的所有指数都假设超声的传播是线性的。事实上，在大多数可能涉及生物效应的暴露条件下，声音传播是高度非线性的。在本研究中已经使用非线性传播模型来评估在诊断过程中遇到的实际暴露条件下发生的效应的性质。由于定义热指数的方式，事实证明，忽略非线性传播导致低估组织温度增量，其通常小于40%。如当前实现的，机械指数可能被低估超过两倍，因为它忽略了由非线性传播引起的声场的饱和。对于软组织中的大传播距离（例如，10 cm，肝脏中3 MHz）;然而，由于这些相同的饱和现象，在物理上难以超过对应于MI > 2的组织压力。版权所有（C）1996世界医学与生物学超声联合会
Formulation of indices that can be used as predictors of biological effects of ultrasound involves a process called derating, in which measurements of the sound field made in water are extrapolated to estimates of the magnitude of the sound fields in the tissues of the body, All indices that have been formulated up to the present time assume that the propagation of ultrasound is linear, In fact, under most exposure conditions for which biological effects may be a concern, sound propagation is highly nonlinear, A nonlinear propagation model has been used in this study to evaluate the nature of the effects that occur under realistic exposure conditions encountered in diagnostic procedures, Because of the way that the thermal index is defined, it turns out that ignoring nonlinear propagation leads to underestimates of tissue temperature increments that typically are less than 40%, As currently implemented, the mechanical index may be underestimated by more than a factor of two because it ignores the saturation of the sound fields that result from nonlinear propagation, For large propagation distances in soft tissues (e.g., 10 cm at 3 MHz in liver); however, it is physically difficult to exceed tissue pressures corresponding to MI > 2 because of these same saturation phenomena. Copyright (C) 1996 World Federation for Ultrasound in Medicine & Biology